反应型受阻胺4-丙烯酰胺基-2，2，6，6-四甲基哌啶（AATP）熔融本体光聚合反应动力学研究

合成了反应型受阻胺4 丙烯酰胺基 2,2,6,6 四甲基哌啶(AATP),用FTIR、1H NMR和元素分析对其结构和组成进行了综合表征.以AATP为聚合单体,利用光 DSC技术研究了AATP熔融本体光聚合反应动力学.结果表明:AATP光聚合的诱导时间随引发剂浓度和辐照光强增加而缩短,光聚合速率随温度的升高而减小;在聚合初期,AATP光聚合速率分别与引发剂浓度和辐照光强的平方根呈较好的线性增长关系.并用稳态和非稳态相结合的光 DSC方法测定了AATP光聚合过程的动力学参数:链增长速率常数kp=2.22—7.96×102L/mol·s、链终止速率常数kt=0.08—2.67×104L/mol·s、表观活化能为Ep-Et/2=-7.70—-13.36kJ/mol、指前因子Ap/At0.5=0.076—0.333(L/mol·s)0.5,kp和kt在聚合初期均随单体转化率的提高而增大,但kt增加的幅度远大于kp.     

多官能度类哑铃形光固化树脂合成及性能

以甲基丙烯酸-β-羟乙酯、异佛尔酮二异氰酸酯、六乙氧基双季戊四醇为主要原料,利用羟基与异氰酸酯的反应,合成出类哑铃型多官能度聚氨酯丙烯酸酯预聚物PUA1~PUA8,用FTIR及1HNMR确证了预聚物结构,用原位红外光谱考察了不同预聚物的光固化动力学。探讨了预聚物结构、体系双键密度对双键转化率、光固化速率及光固化后膜的铅笔硬度、附着力、柔韧性、凝胶率的影响。结果表明,延长丙烯酸酯间的距离,双键的转化率升高,PAU5及PAU1光照20 min后,丙烯酸酯双键的转化率分别为56%及36%。在同样的丙烯酸酯浓度下,适当增加丙烯酸酯官能团间距,可以在保持光固化速率及膜铅笔硬度的同时,提高固化膜的附着力及韧性。PAU5与1,6-己二醇二丙烯酸酯(HDDA)的复配体系光固化后的凝胶率达到99%,固化膜铅笔硬度为6 H,柔韧性可以保持为1.0 mm。     

环氧丙烯酸酯的光固化动力学研究

采用光差扫描量热法考察了环氧丙烯酸酯的光固化动力学行为。实验结果表明，增加光引发剂和活性单体的浓度的都可以使反应的转化率有明显的提升，当光引发剂的质量分数从2％增加到5％，转化率由76．2％上升至88.3％；当活性单体质量分数从15％增加到25％，转化率由73．8％上升至95．3％，但单体质量分数的提高对反应速率的变化不是很明显。此外，光固化反应速率对光强非常敏感，而氧气对丙烯酸酯光固化体系的阻聚作用较弱。     

紫外光固化聚氨酯丙烯酸酯的合成及性能研究

以异佛尔酮二异氰酸酯（IPDI）、季戊四醇三丙烯酸酯（PETA）和丙三醇为原料分步反应合成了可光固化九官能团聚氨酯丙烯酸酯（PUA）预聚物。讨论了温度、时间、催化剂用量对合成PUA预聚物的影响,用红外光谱（FT-IR）对预聚物结构进行了表征,并测试了PUA预聚物紫外光固化膜的附着力、光泽度、硬度等物理性能。结果表明,分步反应合成PUA预聚物时,第一步反应温度为65℃,反应时间为2．5h,且催化剂用量为0．02％;第二步反应温度为75℃,反应时间为2．5h;经紫外光固化所得的PUA固化膜附着力为0级、光泽度为97,硬度为5H,均比市售同类产品高。     

接枝型PUA乳液合成及聚合动力学研究

甲基丙烯酸羟丙酯与水性聚氨酯预聚体反应,得到双烯封端的水性聚氨酯乳液。在乳化剂、引发剂存在下,将丙烯酸酯单体与水性聚氨酯乳液充分混合,并引发聚合,制备了接枝型PUA乳液。TEM观察了PUA乳液的形貌,PUA乳液的粒径在60～120 nm之间;FTIR和NMR表征了合成的PUA结构,显示丙烯酸酯的加入改变了PU本身的氢键相互作用;转化率测试表明,甲基丙烯酸羟丙酯与PU预聚体的反应具有二级动力学特征,而乳化剂的用量影响丙烯酸酯单体与双烯封端聚氨酯乳液的反应速率,反应速率与乳化剂用量符合Rp∝[SDS]0.28。     

EPDM-g-SAN接枝共聚反应的研究

探讨以正庚烷 /甲苯混合物为溶剂 ,采用共聚法制备EPDM接枝聚苯乙烯 丙烯腈 (EPDM g SAN)的反应条件。试验得出的优化反应条件为 :单体苯乙烯 /丙烯腈质量比　 3 /1,EPDM/单体质量比　 45 /5 5 ,引发剂BPO浓度　3 3 8× 10 - 3mol·L- 1 ,正庚烷 /甲苯体积比　 60 /4 0 ,反应温度　 80℃ ,反应时间　 2 0h。在此条件下 ,反应的单体转化率、接枝率和接枝效率分别为 75 % ,3 3 %和 3 6%。红外光谱分析证明 ,EPDM分子链上接枝了SAN支链     

新型芳香二胺扩链剂DMTDA的"原位"扩链反应动力学研究

采用傅立叶变换红外光谱仪(FTIR)法"原位"跟踪了二胺扩链剂2,4/2,6-二氨基-3,5-二甲硫基甲苯(DMTDA)与异氰酸酯扩链反应的过程.实验结果表明,本体聚合反应中,在反应初期低转化率时,反应规律表现为良好的二级动力学关系,给出了反应初期的动力学常数.反应后期高转化率时,反应速率常数受温度影响较大.当温度较低时,反应受扩散控制影响,NCO和NH2反应的二级反应动力学速率常数逐渐变小;温度较高时,反应速率常数变大;DMTDA的本体聚合反应时活化能Ea为26.3 kJ/mol.100℃下DMTDA的反应初期的速率常数为3.7×10-3 kg/mol·s,其活性是MOCA的3.7倍.比较了常见二胺扩链剂的相对反应活性大小.     

樟脑醌／乙二醇-3-吗啡啉基丙酸酯甲基丙烯酸酯引发牙科复合树脂的光聚合动力学研究

采用Photo-DSC研究了樟脑醌（CQ）／乙二醇-3-吗啡啉基丙酸酯甲基丙烯酸酯（EGMPM）可见光引发牙科复合树脂聚合的动力学过程．考察了CQ浓度、EGMPM浓度以及光强对牙科修复复合树脂光聚合动力学的影响．结果表明：增加引发体系的浓度和增加光强都可以增加反应速率和转化率；同时实验结果验证了Rp∝（I0[CQ][EGMPM]）^1／2的动力学关系．     

聚氨酯丙烯酸酯预聚物的合成和性能测试

以甲苯二异氰酸酯(TDI)、聚醚二元醇(NJ-210)和甲基丙烯酸羟乙酯(HEMA)为原料分步反应合成了可光固化聚氨酯丙烯酸酯(PUA)预聚物。讨论了R值、反应时间、反应温度、催化剂用量和甲基丙烯酸羟乙酯(HEMA)用量对合成的PUA的影响,并用红外光谱(FT-IR)对预聚物结构进行了表征。结果表明:分步反应合成PUA预聚物时,第一步反应R值为2.2,反应时间1.5h;第二步反应温度为70℃,催化剂用量为0.3%,且HEMA用量为TDI的1.3(物质的量比)为最佳;用合成的PUA加入HEMA活性稀释剂,光引发剂和其他助剂配制成的紫外光固化胶黏剂固化速度适中、强度高。     

聚己内酯型聚氨酯丙烯酸酯的合成与性能

以丙烯酸羟乙酯(HEA)、异佛尔酮二异氰酸酯(IPDI)和聚己内酯二醇(PCL)为原料合成了聚氨酯丙烯酸酯(PUA)预聚物,加入光固化助剂,用紫外光固化成膜.讨论了催化剂用量和合成温度对合成PUA预聚物的影响,采用红外光谱(FT-IR)和热重分析(TGA)对固化涂膜结构和性能进行了测试.结果表明,PUA封端反应温度为5...     

Photocatalytic activity of AgBr/TiO2 in water under simulated sunlight irradiation

In this paper, the synthesis of AgBr/TiO₂ catalyst and the photocatalytic activity in water under simulated sunlight irradiation were studied. The influence of AgBr content in catalyst and the incident light intensity on the degradation of methyl orange (MO) was investigated. It was found that the initial reaction rate constant was dependent on the relative levels of AgBr content and incident light intensity, ranging between 0.008 min⁻¹ and 0.023 min⁻¹. At higher levels of AgBr content (>9 wt%), MO degradation was exclusively dependent on the incident light intensity, which implied that the excessive AgBr in catalyst had negligible effect on catalyst activity. However, at lower AgBr contents, the reaction rate increased with the increase of incident light intensity, and eventually reached a plateau level, indicating that the degradation of MO was limited by AgBr content. The results from powder X-ray diffraction (XRD) analysis showed that more than 80% of AgBr remained intact after 14 h of irradiation, although metallic silver was also detected.     

聚氨酯丙烯酸酯浸渍固化对淀粉-纤维素复合膜性能的影响

利用聚氨酯丙烯酸酯树脂（PUA）对淀粉-纤维素膜进行改性,以改善材料性能。先以玉米淀粉和纤维素为主要原料,在无机盐氯化锌水溶液中溶解,用流延法制备淀粉-纤维素混合膜（RSC）;再以PUA为浸渍树脂,采用浸渍固化法制备淀粉-纤维素-聚氨酯丙烯酸酯复合膜（RSC-PUA）,考察树脂浓度、光固化时间等因素对复合膜力学性能、吸水性能的影响,并通过扫描电镜、X射线衍射仪、热重分析等手段表征复合膜形貌和结构。实验结果表明：最适宜树脂质量分数为30%,光固化时间为120s;RSC-PUA复合膜比RSC膜拉伸强度提高2.4倍,断裂伸长率提高6倍,吸水率降低了53.6%,热裂解温度增高113℃。以上结果表明,经PUA树脂改性后的复合膜的力学性能、耐湿性、热稳定性提高。     

Attenuation of concentration fluctuations after a quench to a temperature in the single-phase region

Attenuation of concentration fluctuations in a polystyrene/poly(2-chlorostyrene) blend after a quench from a temperature in the spinodal region to one in the single-phase region was studied by using the time-resolved light scattering technique and a scanning electron microscope. The characteristic wave number q_m, where the maximum of the scattered light intensity was located, move towards smaller values during the attenuation process. The corresponding growth of the wave length of the dominant concentration fluctuation was clearly observed by the electron microscope. The scattered light intensities at small wave numbers were found to increase before they attenuated. In the later period the power-law behavior q_m∼t^−0.3 was observed. The exponent was smaller than the value (0.5) obtained on the basis of the non-linear theory by Akcasu and collaborators.     

Zur kinetik der acrylnitril-polymerisation

The heterogeneous bulk polymerization of acrylonitrile initiated by AIBN has been studied by means of an improved dilatometric technique and a new method of analysis, where the initial reaction rate (v_w)₀ results from the intercept of a straight line in a \documentclass{article}\pagestyle{empty}\begin{document}$ \frac {\ln \left( 1 \hbox{---} {\rm U} \right)} {{\rm e}^{{- 0,5} {\rm k}_{\rm s}{\rm t} \hbox{---} 1}}$\end{document} versus t plot. It has been found that the initial reaction rate is proportional to the square root of the initial catalyst concentration S₀. The ratio of the rate coefficients of propagation and termination\documentclass{article}\pagestyle{empty}\begin{document}$\frac { {\rm k}_{\rm a} } { {\rm k}_{ {\rm w}^{2} } } $\end{document} could be calculated from the slope of a straight line passing through the origin in a plot of (v_w)₀ versus \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt { {\rm S}_{0} }$\end{document} and yielded a value of 280 mol 1^?1.     

Investigation of the optical properties of aqueous solutions of silica nanopowders

The optical properties of the silica nanopowder hydrosol (its ability to scatter and absorb light) are investigated. The dependence of the intensity ratio of the light transmitted through the hydrosol to the incident light on the concentration of the nanopowder in the hydrosol is determined.     

Radical polymerization of acrylonitrile initiated by α-picolinium p-chlorophenacylid

The radical polymerization of acrylonitrile (AN) with α-picolinium p-chlorophenacylid (α-PCPY) as initiator using carbon tetrachloride as inert solvent was investigated at 50°C. The polymerization follows ideal kinetics: the exponent values calculated for the initiator and monomer were found to be 0.5 and unity, respectively. A free radical mechanism with bimolecular termination was confirmed by the inhibiting effect of hydroquinone, a radical quencher. The rate of polymerization was a direct function of initiator (α-PCPY) concentraction, monomer (AN) concentration and temperature. The overall activation energy calculated was 56 kJ/mol. The polymerization was favoured by polar solvents and retarded by non-polar solvents.     

多巯基树脂固化聚氨酯丙烯酸树脂的研究

采用凝胶时间测试和实时红外光谱(RT-IR)研究了不同固化剂、稀释剂及促进剂用量对聚氨酯丙烯酸树脂(PUA)/稀释剂二缩三丙二醇二丙烯酸酯(TPGDA)/自制多巯基树脂固化剂(T-41)/促进剂1,8-二氮杂环[5,4,0]-十一烯(DBU)体系固化速度的影响及固化过程中转化率与反应时间的对应关系。结果表明,该体系中,TPG-DA用量存在一最佳值,使体系凝胶时间最短。凝胶时间随烯烃双键/巯基比例的增加而缩短,随促进剂用量的增加而缩短。通过改变各组分配比,体系的固化时间可控制在数分钟到数十分钟之间,实现PUA的快速固化。     

Light-induced variation in phenolic levels in foliage of rain-forest plants

Levels of phenolic secondary metabolites in the leaves of four west African rain-forest plants,Acacia pennata, Cynometra leonensis, Diopyros thomasii, andTrema guineensis, were correlated with incident light intensity at both the inter- and intraindividual level. Enhanced phenolic levels under high light intensity appeared to be due to production of both polyphenolics (condensed and hydrolyzable tannins) and simple phenolics. InTrema guineensis, where it is possible to separate leaves in terms of both their age and the light incident upon them, condensed tannin production progressed differently during the development of sun and shade leaves, suggesting continuing production of new oligomers in the former but not in the latter. The results of this study suggest that the production of phenolics in relation to variation in incident light is a finely tuned process, which must be explained in terms of plant physiology and intermediate metabolism rather than in terms of resource allocation or a direct response to herbivory.     

脂肪酰基谷氨酸钠与十六烷基三甲基溴化铵在水溶液中的相互作用

研究了Ｎ 脂肪酰基谷氨酸钠（ＦＡＧ Ｎａ）与十六烷基三甲基溴化铵（ＣＴＡＢ）混合水溶液的表面活性，测定了不同比例混合水溶液的表面张力—浓度曲线，得出临界胶束浓度及此时的表面张力。应用Ｇｉｂｂｓ吸附公式求出表面总吸附量，根据吸附层及胶束中两表面活性剂分子的相互作用参数公式求出吸附层及混合胶束组成。实验表明，此体系显示了较高的表面活性。     

Molecular ethane adsorption dynamics on oxygen-covered Pt(111)

The dynamics of ethane trapping on Pt(111)-p(2×2)-O were investigated by supersonic molecular beam techniques at a surface temperature of 100 K. The initial trapping probability was measured in the range of incident energy from 10 to 45 kJ/mol and incident angles from 0^° to 60^°. A broad angular distribution of scattered ethane and total energy scaling (E_T cos^0.2) for ethane trapping indicated a corrugated gas–surface potential. Stochastic trajectory simulations employing a potential developed from the trapping of ethane on Pt(111) gives quantitative agreement of the measured initial trapping probabilities over entire ranges of incident energies and angles. Calculations of energy transfer for ethane after the first bounce on Pt(111) and Pt(111)-p(2×2)-O clearly indicate that interconversion of parallel and perpendicular momentum and energy transfer to lattice vibrations account primarily for the differences in trapping probabilities between ethane on the two surfaces. At glancing incidence trapping is not significantly reduced on the oxygen-covered Pt(111) because the parallel momentum appears to be transferred partially to phonons.